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MHD flow and mass transfer of chemically reactive upper convected Maxwell fluid past porous surface

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Applied Mathematics and Mechanics(English Edition) 2012年第7期33卷 899-910页

作者： k. VAJRAVELU k. V. prasad A. SUJATHA 吴朝安 Department of Mathematics University of Central Florida Department of Mathematics Bangalore University Department of Mechanical Engineering The University of Hong Kong

The magnetohydrodynamic （MHD） flow and mass transfer of an electrically conducting upper convected Maxwell （UCM） fluid at a porous surface are studied in the presence of a chemically reactive species. The governing nonlinear partial differential equations along with the appropriate boundary conditions are transformed into nonlinear ordinary differential equations and numerically solved by the keller-box method. The effects of various physical parameters on the flow and mass transfer characteristics are graphically presented and discussed. It is observed that the order of the chemical reaction is to increase the thickness of the diffusion boundary layer. Also, the mass transfer rate strongly depends on the Schmidt number and the reaction rate parameter. Furthermore, available results in the literature are obtained as a special case.

关键词： chemically reactive species upper convected Maxwell (UCM) fluid mag-netohydrodynamic (MHD) flow mass transfer keller-box method

Continuous segregation of binary heterogeneous solids in fluidized beds

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Particuology 2017年第6期15卷 93-100页

作者： M. prasad Babu P.S.T. Sai k. krishnaiah Department of Chemical Engineering Indian Institute of Technology Madras Chennai 600 036 India

Continuous segregation of a binary mixture of heterogeneous （different density） solids is carried out in a gas-solid fluidized bed. We investigate how gas velocity, solids feed rate, flotsam feed composition, bottom discharge pipe diameter, and minimum fluidization velocity ratio of the flotsam to jetsam parti- cles influence the solids holdup, separation factor, and product quality （flotsam purity at the top outlet）. The results are interpreted in terms of solids holdup information. The results indicate that the separation factor decreases when the gas velocity, bottom discharge pipe diameter, flotsam feed composition, or the minimum fluidization velocity ratio increase, while the separation factor increases as the solids feed rate increases. The product quality decreases when the gas velocity, solids feed rate, or minimum fluidization velocity ratio increase, while the product quality increases as the bottom discharge pipe diameter or flot- sam feed composition increase. Correlations for predicting the separation factor and product quality are proposed using a logistic model for individual flotsam feed compositions, which satisfactorily compares with the present experimental data.

关键词： Normal fluidized bed Continuous segregation Heterogeneous particles Separation factorHoldup

Crustal structure and sedimentation history over the Alleppey platform, southwest continental margin of India:Constraints from multichannel seismic and gravity data

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Geoscience Frontiers 2018年第2期9卷 549-558页

作者： P.Unnikrishnan M.Radhakrishna G.k.prasad Department of Earth Sciences Indian Institute of Technology Bombay Flat 3 "Muruga Kripa"

The Alleppey Platform is an important morphological feature located in the kerala-konkan basin off the southwest coast of India. In the present study, seismic reflection data available in the basin were used to understand the sedimentation history and also to carry out integrated gravity interpretation. Detailed seismic reflection data in the basin reveals that:(1) the Alleppey Platform is associated with a basement high in the west of its present-day geometry(as observed in the time-structure map of the Trap Top(k/T boundary)),(2) the platform subsequently started developing during the Eocene period and attained the present geometry by the Miocene and,(3) both the Alleppey platform and the Vishnu fracture zone have had significant impact on the sedimentation patterns(as shown by the time-structure and the isochron maps of the major sedimentary horizons in the region). The 3-D sediment gravity effect computed from the sedimentary layer geometry was used to construct the crustal Bouguer anomaly map of the *** 3-D gravity inversion of crustal Bouguer anomaly exhibits a Moho depression below the western border of the platform and a minor rise towards the east which then deepens again below the Indian shield. The 2-D gravity modelling across the Alleppey platform reveals the geometry of crustal extension,in which there are patches of thin and thick crust. The Vishnu Fracture Zone appears as a crustal-scale feature at the western boundary of the Alleppey platform. Based on the gravity model and the seismic reflection data, we suggest that the basement high to the west of the present day Alleppey platform remained as a piece of continental block very close to the mainland with the intervening depression filling up with sediments during the rifting. In order to place the Alleppey platform in the overall perspective of tectonic evolution of the kerala-konkan basin, we propose its candidature as a continental fragment.

关键词： Gravity Seismic reflection Alleppey platform Rifting Continental fragments Western continental margin of India

Continuous segregation of binary heterogeneous solids in a fast-fluidized bed

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Particuology 2017年第6期15卷 101-107页

作者： M. prasad Babu P.S.T. Sai k. krishnaiah Department of Chemical Engineering Indian Institute of Technology Madras Chennai 600 036 India

Continuous segregation of binary heterogeneous solids （different density mixtures） is carried out in a gas-solid fluidized bed to study the effects of gas velocity, solids feed rate, feed composition and density difference of solids on the separation factor （recovery of flotsam at top outlet） and the quality of the product （purity of flotsam at top outlet） in a continuous fast-fluidized bed. The holdup of the bed material is obtained in each experimental run. It is observed that the separation factor decreases with increase in solids feed rate or density difference of solids, and increases with gas velocity or proportion of flotsam in the feed. The quality of the product decreases with increase in gas velocity or solids flow rate, and increases with feed composition or density difference of solids. The experimental results show that the separation factor and the quality of the product are more sensitive to gas velocity than to other operating parameters, Empirical correlations for predicting the separation factor and quality of the product are proposed based on the Richards model for individual flotsam mass fraction in the feed, and the predictions agree satisfactorily with the present exlgerimental data,

关键词： Fast-fluidized bed Gas-solid Continuous segregation Heterogeneous solids Solids holdup

Role of schorl’s electrostatic field in discoloration of methyl orange wastewater using schorl as catalyst in the presence of H_2O_2

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Science China(Technological Sciences) 2010年第11期53卷 3014-3019页

作者： Murari prasad Environmental Chemistry Division Advanced Materials and Processing Research Institute (C.S.I.R.)

Dyeing wastewater containing methyl orange (MO) could be effectively discolored by schorl-catalyzed Fenton-like system. Experimental results indicated that the MO discoloration ratios could be increased by increasing schorl dosage, temperature, initial H2O2 concentration, and by decreasing solution pH. When the raw schorl and the schorl samples sintered at 750°C, 850°C, 950°C and 1050°C were used as catalyst in Fenton-like system, the MO discoloration ratios obtained were 82%, 31%, 30%, 31% and 7%, respectively. XRD results showed that samples sintered at 750°C, 850°C and 950°C had no change in structure and still held the crystal structure of schorl and quartz, but, the content of schorl crystal decreased. Whereas, schorl crystal completely disappeared in the sample sintered at 1050°C and two new crystal phases of hematite and spinel were formed, which resulted in disappearance of the spontaneous ‘electrostatic poles’. Hence, it was inferred that the electrostatic field of schorl crystal could enhance the MO discoloration by schorl-catalyzed Fenton-like reaction.

关键词： schorl methyl orange discoloration Fenton-like system polarization

Discoloration of Rhodamine B dyeing wastewater by schorl-catalyzed Fenton-like reaction

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Science China(Technological Sciences) 2009年第10期52卷 3054-3060页

作者： Murari prasad Environmental Chemistry Division Advanced Materials and Processing Research Institute (C.S.I.R.)

As other natural iron-bearing minerals, schorl could be taken as an effective iron source for degradation of organic pollutants by mineral-catalyzed Fenton-like system. In our present study, the schorl-catalyzed Fenton-like system has been successfully developed for discoloration of an active commercial dye, Rhodamine B (RhB), in an aqueous solution. Through a number of batch discoloration experiments under various conditions, it was found that the reactivity of the system increased by, respectively, increasing schorl dosage, temperature, hydrogen peroxide starting concentration and by decreasing the pH. Over 90% of discoloration ratio could be gained in less than 30 min, and nearly 70% of total organic carbon (TOC) could be removed in less than 200 min. And, the schorl catalyst could be repeatedly used at least ten times, still with high catalytic activity. Comparative studies indicated that the RhB discoloration ratios were much higher in presence of schorl and H2O2 than those in presence of schorl or H2O2 only, which suggested that the schorl-catalyzed Fenton-like reaction governed the RhB discoloration process. The content of Fe ion leaching in the solution was also measured using inductively coupling plasma-atomic emission spectra (ICP-AES). A mechanism proposed herein suggested that adsorption and Fenton-like reaction (heterogeneous and homogeneous) were responsible for the discoloration of RhB.

关键词： schorl Rhodamine B discoloration Fenton-like reaction

Numerical investigations on HCCI engine with increased induction induced swirl and engine speed

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Journal of Central South University 2015年第10期22卷 3837-3848页

作者： T.karthikeya Sharma G.Amba prasad Rao k.Madhu Murthy Department of Mechanical Engineering NIT

Homogeneous charge compression ignition(HCCI) mode of combustion is popularly known for achieving simultaneous reduction of NOx as well as soot emissions as it combines the compression ignition(CI) and spark ignition(SI) engine features. In this work, a CI engine was simulated to work in HCCI mode and was analyzed to study the effect of induction induced swirl under varying speeds using three-zone extended coherent flame combustion model(ECFM-3Z, compression ignition) of STAR-CD. The analysis was done considering speed ranging from 800 to 1600 r/min and swirl ratios from 1 to 4. The present study reveals that ECFM-3Z model has well predicted the performance and emissions of CI engine in HCCI mode. The simulation predicts reduced in-cylinder pressures, temperatures, wall heat transfer losses, and piston work with increase in swirl ratio irrespective of engine speed. Also, simultaneous reduction in CO2 and NOx emissions is realized with higher engine speeds and swirl ratios. Low speeds and swirl ratios are favorable for low CO2 emissions. It is observed that increase in engine speed causes a marginal reduction in in-cylinder pressures and temperatures. Also, higher turbulent energy and velocity magnitude levels are obtained with increase in swirl ratio, indicating efficient combustion necessitating no modifications in combustion chamber design. The investigations reveal a total decrease of 38.68% in CO2 emissions and 12.93% in NOx emissions when the engine speed increases from 800 to 1600 r/min at swirl ratio of 4. Also an increase of 14.16% in net work done is obtained with engine speed increasing from 800 to 1600 r/min at swirl ratio of 1. The simulation indicates that there is a tradeoff observed between the emissions and piston work. It is finally concluded that the HCCI combustion can be regarded as low temperature combustion as there is significant decrease in in-cylinder temperatures and pressures at higher speeds and higher swirl ratios.

关键词： HCCI engine ECFM-3Z swirl ratio emissions and performance

Blood electrolytes of the freshwater catfish Heteropneustes fossilis in response to treatment with a botanical pesticide(latex of Euphorbia royleana)

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Integrative Zoology 2011年第2期6卷 150-156页

作者： ManiRam prasad Abhishek kUMAR Diwakar MISHRA Sunil k.SRIVASTAV Ajai k.SRIVASTAV Department of Zoology D.D.U Gorakhpur UniversityGorakhpur 273009India

The aim of the present study was to determine changes in blood electrolytes(calcium and phosphate)in the freshwater catfish Heteropneustes fossilis following short-and long-term exposure to latex of Euphorbia *** investigate the effects of short-term exposure,fish were exposed to 80%of the 96-h LC_(50) of *** latex(2.47 mg/L)for 96 *** assess the effects of long-term exposure,fish were exposed to 20%of the 96-h LC_(50) of *** latex(0.618 mg/L)for 28 *** were killed after 24,48,72 and 96 h(short-term experiments)or after 7,14,21 and 28 days(long-term experiments).Blood samples were collected and sera were analyzed to determine calcium and inorganic phosphate *** calcium levels decreased progressively in *** after 48 h exposure to *** *** decrease persisted until the end of the experiment(96 h).Serum inorganic phosphate levels in treated fish decreased progressively from 72 *** 7 days exposure to *** latex,decreased serum calcium levels were noted in *** that persisted until the end of the *** phosphate levels were decreased in *** on days 21 and 28 of exposure to *** *** is concluded that *** latex alters the blood electrolyte content of the *** change in these electrolytes,particularly calcium levels,may cause disturbances in the normal vital physiological functions of the fish,its growth rate,and even its ability to survive in nature.

关键词： blood calcium blood phosphate Euphorbia royleana Heteropneustes fossilis

Control of peak pressures of an HCCI engine under varying swirl and operating parameters

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Frontiers in Energy 2016年第3期10卷 337-346页

作者： T. kARTHIkEYA SHARMA G. AMBA prasad RAO k. MADHU MURTHY Department of Mechanical Engineering NIT Warangal Warangal506004 India

The major advantages of homogeneous charge compression ignition （HCCI） are high efficiency in combination with low NOx-emissions. However, one of the major challenges with HCCI is the control of higher peak pressures which may damage the engine, limiting the HCCI engine life period. In this paper, an attempt is made to analyze computationally the effect of induction swirl in controlling the peak pressures of an HCCI engine under various operating parameters. A single cylinder 1.6 L reentrant piston bowl diesel engine is chosen. For computational analysis, the ECFM-3Z model of STAR - CD is considered because it is suitable for analyzing the combustion processes in SI and CI engines. As an HCCI engine is a hybrid version of SI and CI engines, the ECFM- 3Z model with necessary modifications is used to analyze the peak pressures inside the combustion chamber. The ECFM-3Z model for HCCI mode of combustion is validated with the existing literature to make sure that the results obtained are accurate. Numerical experiments are performed to study the effect of varying properties like speed of the engine, piston bowl geometry, exhaust gas recirculation （EGR） and equivalence ratio under different swirl ratios in controlling the peak pressures inside the combustion chamber. The results show that the swirl ratio has a considerable impact on controlling the peak pressures of HCCI engine. A reduction in peak pressures are observed with a swirl ratio of 4 because of reduced in cylinder temperatures. The combined effect of four operating parameters, i.e., the speed of the engine, piston bowl geometry, EGR, and equivalence ratio with swirl ratios suggest that lower intake temperatures, reentrant piston bowl, higher engine speeds and higher swirl ratios are favorable in controlling the peak pressures.

关键词： HCCI engine ECFM-3Z Swirl ratio peak pressures engine speed piston bowl geometry